AWD vs 4WD: explanation, types, pros and cons of each type

A crucial factor when choosing a car is the type of drivetrain. Either used for an everyday commute to work in the city or for an offroad adventure on rough mountain terrains, the car's behavior and performance are tied up to its drivetrain and its capabilities. That's why it is very important for the driver to make a clear distinction between two of the most popular drivetrain types: AWD and 4WD.

What's an All-wheel-drive system?

The All-wheel drive system (known also as an AWD, for short) is known for powering simultaneously both front and rear wheels of the vehicle. However, AWD can be divided into two sub-types. The first one, called full-time AWD, continuously drives the vehicle's wheels. The other one, called part-time or automatic AWD, works as a 2WD during most of the time with the 4WD kicking in when the need for more traction control calls.

How exactly the All-wheel drive system works?No matter which sub-type of the All-wheel drive we have, neither one of them needs the driver's control over them in order to function properly. There are some modern systems that enable the person behind the wheel to control the power distribution between the wheels, but in the majority of cases, there's no need for such actions.

What's specific for the all-wheel drive is that the torque is distributed between each of the four wheels via a multitude of differential and viscous couplings or clutches – helping the traction optimization.

Let's get a look into the sub-types of the AWD.

What is full-time AWD and how it works?

The full-time AWD utilizes both front and rear axles continuously. It improves the vehicle's handling and performance equally on both - dry pavement and slippery road conditions.

What is a part-time AWD and how it works?

The interesting side of this type of drivetrain is that it powers either the front or the rear wheels when working in normal conditions. When additional traction is needed, the other two wheels automatically tune in. That's possible thanks to a variety of electronic sensors, which detect, gather, process and directly send information to the drivetrain's computer.

The latter chooses when is the exact moment and what is the amount of power that needs to be transmitted to each of the four wheels.

Pros:

  • it does not need the driver's assistance to operate properly. Most modern cars come with a refined AWDs which are capable to decide on their own if there's a need for a 2WD or an AWD. 
  • easy to implement, it's no wonder that is one of the most common types of drivetrains in the modern automotive industry: from sedans to sports cars and SUVs. 
  • the system automatically adapts itself to the road conditions
  • it's a perfect choice for both slow and highway speeds

Cons:

  • due to its complicated engineering technology, it adds an additional amount of money to the price tag of the car
  • since most of the operating time the system uses all four wheels of the vehicle, the tires tend to wear out faster than expected
  • this type of drivetrain limits the vehicle's offroad abilities
  • the system itself is quite heavy, meaning a few extra kilos are added to the vehicle's weight. this automatically increases fuel consumption.

What's a 4WD system?

The 4WD is probably one of the most popular and best-known types of drivetrains. It's commonly used in heavy-duty trucks and pickups (made for both offroad adventures and towing, and transportation of heavy objects). Typical for that kind of vehicles are the reinforced underbody, big-sized tires, tow hook, and higher ground clearance.

And just like the AWD system, the 4WD can also be divided into sub-types: part-time and full-time. Unlike the AWD, this drivetrain offers the driver control over the power distribution via an electric or mechanical lever.

What is a full-time 4WD system and how it works?

The process is almost the same as in the AWD - power is continuously transmitted to each of the vehicle's wheels. However, depending on the machine's model and the drivetrain's design, the driver can control the way and the amount of power supplying the front and rear set of wheels.

What is a part-time 4WD?

Frequently used in huge SUVs and heavy-duty pickups, the part-time 4WD is ideal for extreme road and climate conditions. By default, the part-time 4WD utilizes either the front or the rear wheels. If the situation calls, the driver has the option to switch on all four wheels of the automobile. It's also possible for the driver to lock the differentials in order to maximize the traction in extreme offroad conditions.

There are two more sub-types of the 4WD, called a shift-on-the-fly and an automatic 4WD. The first one offers the driver the ability to switch between a 2WD to 4WD while the vehicle is still in motion. The second one reduces the fuel consumption thanks to electric sensors that gather information and transfer it to the system's computer that controls whether or not the 4WD is needed.

Pros:

  • perfect for an offroad driving

Cons:

  • most common among the heavy-duty vehicles and huge SUVs- could attribute to a significant increase in noise and vibrations
  • according to some drivers, the 4WD offers quite stiff driving experience compared with the 2WD when used on a dry pavement
  • the 4WD adds extra weight to the vehicle, plus increases the fuel consumption
  • the 4WD adds to the final price tag of the car

 


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